I. Field of the Invention
This invention relates generally to alarm systems for indicating to the occupants of a second vehicle the proximity of a first vehicle. More particularly, this invention relates to an alarm system wherein a first vehicle's strobe light or laser light source activates indicators in a second vehicle to alert the occupants of the second vehicle to the proximity of the first vehicle.
II. Discussion of the Prior Art
Many modern vehicle passenger compartments are designed and built to be quiet when their windows are closed. Outside noises coming from car horns and radios are prevented from entering the passenger compartment and distracting the driver. Unfortunately, emergency vehicle sirens and train whistles are also prevented from entering the passenger compartment. Car radios or sound systems played at moderate levels inside the vehicle make it even more difficult to hear outside alarms. Thus, an emergency vehicle siren or a train whistle may be undetected by the occupants of a vehicle. This creates a hazardous situation on the highways.
Emergency vehicles need an unobstructed path to respond to an emergency within an acceptable time frame. The occupants of the emergency vehicle need to be able to change traffic signals and alert the drivers of other vehicles to the presence of the emergency vehicle. In the past, radio frequency energy has been used to alert the occupants of one vehicle to the presence of another vehicle. Radio frequency signals were transmitted from one vehicle and detected by an unsuspecting second vehicle. Upon detection, a warning signal was generated in the second vehicle. The warning signal was transmitted over the radio or through independent audio and visual components. This method is shown in U.S. Pat. No. 3,854,119, issued to Friedman et al, and U.S. Pat. No. 3,876,940, issued to Wickord et al.
The Friedman patent describes receiving and identifying amplitude modulated signals to operate switching means for activating devices such as audio speakers, light emitting diodes, panel displays or neon lights in relation to the amplitude of the received signals. The Wickord patent discloses a warning device utilizing radio transmission on an assigned frequency having a transmitter in the emergency vehicle and a receiver in the regular vehicle. One feature of the Wickord patent is the conversion of the received signal to the intermediate frequency of a radio receiver, muting the broadcast reception on the radio or turning the radio on (if it is off), and applying a warning signal through the radio system. In each of these patents, the activating radio frequency energy is transmitted in all directions. Radio frequency energy, however, is not easily blocked by buildings or other objects.
In a rural area, where few emergencies occur and few trains travel, an occasional interruption by a train or emergency vehicle alarm signal may be acceptable. However, in a city or suburban environment, emergencies occur more frequently. Constant interruption of the radio and subsequent distraction of the driver due to an emergency occurring many blocks away may create a hazard. Thus, a signal limited in range by objects in its path is desired. It is also desirable to change traffic signals in the immediate vicinity of the emergency vehicle. Neither the Friedman nor the Wickord patent disclose anything about changing traffic signals to accommodate an emergency vehicle and both use radio frequency energy.
To be useful in cities and suburbs, the energy transmitted by the emergency vehicle's alarm system must be limited to the immediate vicinity. The system should regulate traffic flow by changing traffic signals and alerting the drivers of vehicles to the presence of an emergency vehicle. The present invention meets these needs by using a strobe light or laser light source situated on an emergency vehicle or train. The light signal is detectable on a line of sight basis. Thus, if an emergency is occurring many blocks away and the second vehicle is not in the line of sight of the emergency vehicle, the audio and visual warning indicators in the second vehicle will not be activated.
Light has been used in the past to change traffic signals to accommodate emergency vehicles. One such system is described in U.S. Pat. No. 2,457,502, issued to Shepherd. The Shepherd patent discloses the use of modulated polarized light signals to selectively effect remote control operations by means of light or similar energy. One application described in the Shepherd patent is the use of polarized and modulated light to cause a control mechanism to function and result in the production of a predetermined traffic signal at an intersection. A system much simpler than this for changing traffic signals is currently offered by 3M and includes a High or Low Priority Emitter Assembly strobe light and the Opticom.RTM. brand detector installed at signalized intersections. A strobe light signal from an emergency vehicle is detected by the Opticom.RTM. detector and the traffic signal is changed to allow the emergency vehicle to pass through.
By using a 3M High or Low Priority Emitter Assembly, or similar strobe light to activate the alarm system of the present invention, an integrated system, that changes traffic signals and alerts drivers, can be implemented. The emergency vehicle needs only one transmitting strobe light for alerting the drivers of other vehicles and changing traffic signals to accommodate safe passage.
From the above analysis, it can be seen that the prior art references of which we are aware, individually and as a whole, do not disclose an emergency vehicle alarm system using a strobe light or laser light source to alert the occupants of an unsuspecting vehicle of an emergency vehicle on-call in the area.